1. Field of the Invention
This invention relates to an automatic iris control system to control the opening and closing of an adjustable iris to apply an optical image having a preselected light intensity level upon the surface of an imaging recording device and more particularly to an automatic iris control system having a feedback control circuit wherein a light intensity information signal is developed from a video signal produced by the video camera to dynamically adjust an iris in response to variations in the reflected light from a subject received by the optical input device to apply an optical image at a desired intensity level on the surface of an electronic imaging means of a video camera.
2. Description of the Prior Art
Use of an adapter with the automatic diaphragm setting iris is known in the art. The automatic diaphragm setting device known in the art includes a plurality of discrete settings which are adapted to change the light intensity of the image applied to a recording device such as a 16 mm camera. In operation, the automatic diaphragm is positioned between the camera and the input optical device and the reflected optical image is applied to a photo-conductive cell in the camera. The photo-conductive cell measures the light and, by means of an exposure control and intensification system, the photo-conductive cell controls a motor which operates the aperture diaphragm.
Another known adjustable iris system includes a manually adjustable iris wherein the operator manually adjusts the opening of the iris in order to manually set the intensity of the optical image being recorded by the camera.
It is also known in the prior art to use video sensing of the video information portion of a composite video signal to control light intensity. The known video sensing systems include detection circuits which are responsive to either peaks as average video signal information.